We should check our driver first
$ cd /opt/Qt5.2.1/5.2.1/gcc_64/plugins/sqldrivers
then we can find some files
Use the command below to check library
$ ldd libqsqlmysql.so
if you find the problem libmysqlclient_r.so.16 => not found
it may be the library-dependency problem.
After I did a little research on the Internet, there is a way would be easy.
$ cd /usr/lib/x86_64-linux-gnu
if you find libmysqlclient_r.so.18
,
$ cp libmysqlclient_r.so.18 libmysqlclient_r.so.16